Field of the Invention
The present invention relates to an error detection apparatus for clock-synchronized serial communication and, more particularly, to a data communication system between a control unit and printhead of an inkjet printing apparatus or the like, a data transmission apparatus, and a data reception apparatus.
Description of the Related Art
An inkjet printing apparatus has used clock-synchronized serial communication for communication between a control device and a printhead. The size of discharge nozzles in the printhead has been decreased to improve the printing quality, and the transfer data rate of communication has been increased to increase the printing speed. A transfer clock frequency increases in proportion to the transfer data rate. This may impose a problem associated with radiation noise in a transmission line. Low voltage differential signaling (LVDS) is effective to suppress radiation noise. However, LVDS is readily influenced by ambient noise, thereby readily causing a bit error in the transmission line. Bit error detection is performed in the printhead for more reliable data transfer. However, it is common practice to add an error detection bit (for example, a parity bit or CRC detection bit) to transfer data for error detection, and thus the data transfer efficiency deteriorates in accordance with the added bit, and the effective rate of data transfer decreases. Japanese Patent Laid-Open No. 2007-267392 discloses an apparatus and method in which an error detector and a decoder for decoding encoded data bits are arranged in a physical layer and an error detection code is efficiently transferred in point-to-point communication between integrated circuits. Japanese Patent Laid-Open No. 2007-267392 has as its object to implement reliable data communication between electronic apparatuses by this transfer operation.
Encoding described in Japanese Patent Laid-Open No. 2007-267392 is generally known as 8B/10B, and a clock is embedded in an encoded data bit group. Thus, the decoder has a relatively large circuit scale. Consequently, it is difficult to apply the technique described in Japanese Patent Laid-Open No. 2007-267392 to a device formed by a small-scale circuit like the printhead in the inkjet printing apparatus.